Wallabies coach Michael Cheika defiant despite Scotland thumping

A defiant Michael Cheika insists his Wallabies side are progressing well ahead of the 2019 Rugby World despite slumping to a record-breaking loss to Scotland.

Reduced to 14 men following Sekope Kepu's red card for a shoulder charge to the head of Hamish Watson on the stroke of halftime, the impressive Scots took full advantage to run in eight tries on their way to a 53-24 win.

The Murrayfield mauling was the biggest victory by Scotland over a southern hemisphere nation and comfortably eclipsed their previous largest winning margin of nine points against the Wallabies in 1981.

Kepu's dismissal turned the match on its head, with the Wallabies leading 12-10 at the time following two quickfire tries from Tevita Kuridrani.

Gregor Townsend's side immediately took advantage of their numerical advantage with a try from halfback Ali Price giving them a 17-12 lead at the break.

French referee Pascal Gauzere had no option to send Kepu from the field after referring the incident to television match official Graham Hughes who recommended a red card be shown.

Kepu's red card was only the fifth handed to a Wallabies player and the first since Kuridrani was dismissed for a lifting tackle against Ireland in 2013.

The match was decided by four tries in a dazzling 15-minute second-half spell that sent the home crowd into a frenzy.

Cheika did not disagree with the decision but refused to single Kepu out for any blame.

"I don't think it was the story of the game. I thought we still could have won with 14 to be honest," Cheika said.

"The referee really didn't have much alternative. But just for a point of view for Kepu, he's got no intent to take the player in the head.

"The player when you watch him, his back leg slips underneath him, so he gets lowered, he goes low, lower than where Kepu is aiming and it's going to show that that's where the contact was made but there's no intent ... to go there."

Despite being blown away by the impressive home side, Cheika insists his team is still a work in progress with Queensland Reds prop Taniela Tupou becoming the latest debutant since the 2015 World Cup.

"We're over here with about 10 or 12 guys that aren't he but could be in in the mix for this squad without a doubt," he said.

"Over the last two years we've looked to add some depth to our squad which we didn't have.

"We had our 27th debutant since the World Cup. A lot of those guys are in and around the squad.

"Maybe we are too young? A big thing for us is to look to improve our mindset.

"Get away from not fully believing we can do the job regardless of the conditions.

"I think we've worked really well about not using excuses for ourselves and taking the hard road as we have all year and that will come back and tell for us for sure."